Dirt-repellent coatings are designed to confer protection from soiling on substrates coated therewith. The soiling proclivity of porous or absorbent substrates, such as wood, concrete, natural stone or artificial stone, is particularly pronounced, especially on contact with liquids, particularly with colored liquids, such as coffee, tea or oils. Soiling here takes the form of colored stains being formed on the substrate due to extraction of colored substances out of the substrate or due to importation of colored substances into the substrate. Different dirt-repellent coatings have been proposed in an effort to preempt such problems. EP-A 1 926 787 for instance teaches coating media based on polymer latex binders comprising phosphoric esters as anionic emulsifiers. WO-A 98/10026 similarly teaches therefor anionically stabilized polymers of styrene, acrylic esters and also ethylenically unsaturated carboxylic acids. WO-A 2011/128232 recommends improving the soiling resistance of cementitious coatings by sprinkling dry building materials comprising redispersible polymeric powders onto not yet fully set cementitious substrates.
Alternatively, it has also been proposed that the ability to wash off stains be improved by modifying the coatings with additives. DE-A 197 07 219 therefor teaches aqueous coating media comprising not only some film-forming organic polymers but also low molecular weight organosilicon compounds as essential component.
Dirt-repellent and washable paints have likewise been intensively described. EP-A1 0 614 955 for instance teaches styrene-acrylate copolymers useful as additives for paints. EP-A 1 732 997 recommends improving the pigment-binding capacity and the wet abrasion resistance of pigmentary coatings by the addition of polymers based on specified amounts of so-called hard and soft monomers and also ethylhexyl acrylate and acid-functional monomers.
Yet it continues to be a problem to provide coatings which protect the substrates from soiling in the event of contract with various liquids, for example contact with hydrophobic and/or hydrophilic liquids, such as coffee, tea, ketchup, fats or oils, i.e., particularly substances from the food sector. This problem setting is particularly acute with porous or absorbent substrates or on contact with warm or even hot liquids.